import java.util.ArrayDeque;
import java.util.Deque;
import java.util.HashSet;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.ReentrantLock;

/**
 * @author zhou, xin
 * @date 2021/5/10 17:23
 */
public class MyThreadPool {
    public static void main(String[] args) {
        ThreadPool threadPool = new ThreadPool(10,
                2, TimeUnit.MILLISECONDS, 10, ((queue, task) -> {
            // 1）死等
//            queue.put(task);
            // 2）带超时等待
            // queue.offer(task, 1500, TimeUnit.MILLISECONDS);
            // 3）让调用者放弃任务执行
//            System.out.println("放弃");
            // 4）让调用者抛出异常
//            throw new RuntimeException("任务执行失败" + task);
            // 5）让调用者自己执行任务
//            task.run();
        }));
        for (int i = 0; i < 5; i++) {
            int j = i;
            threadPool.execute(() ->{
                System.out.println(j);
            });
        }
    }
}

@FunctionalInterface
interface RejectPolicy<T> {
    void reject(BlockingQueue<T> queue, T task);
}

class ThreadPool {
    // 任务队列
    private BlockingQueue<Runnable> taskQueue;

    // 线程集合
    private HashSet<Worker> workers = new HashSet<>();

    // 核心线程数
    private int coreSize;

    // 获取任务的超时时间
    private long timeout;

    private TimeUnit timeUnit;

    private RejectPolicy<Runnable> rejectPolicy;

    // 执行任务
    public void execute(Runnable task) {
        // 当任务数没有超过核心数（coreSize）时，直接交给worker对象执行
        // 如果任务数超过coreSize时，加入任务队列暂存
        if (workers.size() < coreSize) {
            Worker worker = new Worker(task);
            workers.add(worker);
            worker.start();
        } else {
            //taskQueue.put(task);
            taskQueue.tryPut(rejectPolicy, task);
        }
    }

    public ThreadPool(int coreSize, long timeout, TimeUnit timeUnit, int queueCapcity,RejectPolicy<Runnable> rejectPolicy) {
        this.taskQueue = new BlockingQueue<>(queueCapcity);
        this.coreSize = coreSize;
        this.timeout = timeout;
        this.timeUnit = timeUnit;
        this.rejectPolicy = rejectPolicy;
    }

    class Worker  extends Thread{
        private Runnable task;

        public Worker(Runnable task) {
            this.task = task;
        }

        @Override
        public void run() {
            // 执行任务
            // 1）当task不为空，执行任务
            // 2）当task执行完毕，再接着从任务队列获取任务并执行
            //  while (task != null || (task == taskQueue.take()) != null) { // 死等，下面的超时结束线程
            while (task != null || (task = taskQueue.poll(timeout,timeUnit)) != null) {
                try {
                    task.run();
                } catch (Exception e) {
                    e.printStackTrace();
                } finally {
                    task = null;
                }
            }
            synchronized (workers) {
                workers.remove(this);
            }
        }
    }
}

class BlockingQueue<T> {
    // 1.任务队列
    private Deque<T> queue = new ArrayDeque<>();

    // 2.锁
    private ReentrantLock lock = new ReentrantLock();

    // 3.生产者条件变量
    private Condition fullWaitSet = lock.newCondition();

    // 4.消费者条件变量
    private Condition emptyWaitSet = lock.newCondition();

    // 5.容量
    private int capacity;

    public BlockingQueue(int capacity) {
        this.capacity = capacity;
    }

    // 带超时的等待
    public T poll(long timeOut, TimeUnit unit) {
        lock.lock();
        try {
            // 将timeOut统一转换为纳秒
            long nanos = unit.toNanos(timeOut);
            while (queue.isEmpty()) {
                try {
                    // 返回剩余的时间
                    if (nanos <= 0) {
                        return null;
                    }
                    nanos = emptyWaitSet.awaitNanos(nanos);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            T t = queue.removeFirst();
            fullWaitSet.signal();
            return t;
        } finally {
            lock.unlock();
        }
    }

    BlockingQueue() {
    }

    // 阻塞获取
    public T take() {
        lock.lock();
        try {
            while (queue.isEmpty()) {
                try {
                    emptyWaitSet.await();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            T t = queue.removeFirst();
            fullWaitSet.signal();
            return t;
        } finally {
            lock.unlock();
        }
    }

    // 阻塞添加
    public void put(T task) {
        lock.lock();
        try {
            while (queue.size() == capacity) {
                try {
                    fullWaitSet.await();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            queue.addLast(task);
            emptyWaitSet.signal();
        } finally {
            lock.unlock();
        }
    }

    // 带超时时间阻塞添加
    public boolean offer(T task, long timeout, TimeUnit timeUnit) {
        lock.lock();
        try {
            long nanos = timeUnit.toNanos(timeout);
            while (queue.size() == capacity) {
                try {
                    if (nanos <= 0) {
                        return false;
                    }
                    nanos = fullWaitSet.awaitNanos(nanos);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            queue.addLast(task);
            emptyWaitSet.signal();
            return true;
        } finally {
            lock.unlock();
        }
    }

    // 获取大小
    public int size() {
        lock.lock();
        try {
            return queue.size();
        } finally {
            lock.unlock();
        }
    }

    public void tryPut(RejectPolicy<T> rejectPolicy, T task) {
        lock.unlock();
        try {
            // 判断队列是否满
            if (queue.size() == capacity) {
                rejectPolicy.reject(this, task);
            } else { // 有空闲
                queue.addLast(task);
                emptyWaitSet.signal();
            }
        } finally {
            lock.unlock();
        }
    }
}